Sealing-in method



I Oct. 3, 1944. A. J. WHITE SEALING-IN METHOD Original Filed Nov. 27,1957 Inventor: Arthur J. White b W 9 His A ttorneg. I

Patented Oct. 3, 1944 SEALING-IN METHOD Arthur J. White, ClevelandHeights, Ohio, assignor-to General Electric Company, a corporation ofNew York Application November 27, 1937, Serial No. 176,910

Renewed January 11, 1940 7 Claims.

My invention relates to an improved method of sealing together the endsof tubular glass members, and more particularl to a method of sealingglass stems in the bulbs or envelopes of electric lamps or similardevices.

Stems for electric lamps and similar devices generally comprise a glassstem tube having one end fused around a portion of one or more leadinwires extending through the tube, the other end of said tube beingflared or flanged outward. The stem is sealed in a bulb or envelope byinserting it therein and then applying gas flames to fuse the open endor neck portion of said bulb or envelope and the flange on said stem toseal them together.

The above method has the disadvantage in some instances that the gasflames distort a considerable portion of the bulb or envelope adjacentto the seal. This may be objectionable for several reasons, one of whichis that the subsequently attached base may not be properly seated on thebulb. Moreover, the gas flames may, in some instances, adversely affectthe lead-in wires extending from the stem.

One of the objects of the present invention is to provide a new andimproved method of sealing a stem in anenvelope which will obviate theabove-mentioned disadvantages and will seal a stem in an envelopewithout distortion of the portion of the envelope adjacent to the sealedjoint. Another object is to provide a method by which the stem isquickly and efliciently sealed in the envelope to produce a hermeticalseal free from cracks. Other objects and advantages of my invention willappear from the following descripof the lamp with a base attachedthereto.

According to my invention, the method of sealing consists generally inplacing a stem with its flanged end resting on a disc or ring of amaterial which is capable of being heated by induction and will notadhere to the fused glass, such as carbon. The envelope is then placedover the stem with its open end or neck portion resting on the flange oradjacent thereto. .The .said disc or ring is then heated to a highdegree by induction to cause the adjacent ends of the stem and envelopeto be fused and sealed together by conduction and radiationof heat fromthe said disc or ring. Pressure may be applied at the opposite end ofthe envelope, if desired, to press the fused ends of the envelope andstem thereagainst.

Referring to Fig. 1, the lamp illustrated therein in process of assemblycomprises a tubular glass envelope l0 having a stem l l at its upper end(shown as already sealed in), and another stem I2 at its lower end aboutto be sealed in. The

said stem I2 is of the so-called tipless variety and comprises a glassstem tube 13 and an exhaust tube [4 which are fused at their upper endsto form a mass of glass [5 enclosing portions of lead-in wires ill-i6,there being an axial opening I'l through the said mass of glass formedby blowing through the said exhaust tube 54. An electrode l8,consistingpreferably of a coiledcoil of tungsten wire coated with anelectron emissive material such as barium and/or, strontium oxide, issecured at its ends to the inner ends of the lead-in wires l6l6. It isvery desirable that the stemsbe as short as possible in order that theelectrodes Ella-l8 may be close to the ends of the envelope l0.Therefore, in making the stem l2 it is held in an upright position andthe upper ends of the stem tube 13 and exhaust tube M are heated tofusion by gas flames, causing them to collapse and flow down along thelead-in wires lB-IB to form the solid mass of glass 15. While the glassmass I5 is stillplastic, air pressure is applied to the exhaust tube illto blow the opening 11, there being no compression or pressing of theglass mass i5 by a pair of jaws at any time as is the usual presentpractice. Air-is also blown into the space between the exhaust tube l4and stem tube l3 to round out the joint therebetween, therebyeliminating sharp corners which may lead to cracks. During the flowingof the glass downward along the lead-in wires !6--I6, the said wires arecoated with a layer of glass, and breaking off this coating leaves aclean surface, free from oxide, to which the ends of the electrode l8may be readily welded. The stem II is made in the same manner except, ofcourse, that the exhaust tube I4 is omitted. This method of making thestems is described and claimed in my application No. 176,909, of evendate, now Patent 2,128,173. Of course, stems made according to standardpractice may be used if desired.

For sealing in the stem 12, I have illustrated in Fig. 1 an apparatuscomprising a support 'rod or block I 9 of refractory insulatingmaterial, such as sillimanite, having a disc or ring 20 of materialwhich is capable of being heated by induction and will not adhere toglass, preferably carbon. placed on its upper end. The stem I2 isplacedwith its flanged end 2| resting on the disc 20 in abuttingrelation therewith, the exhaust tube II and lead-in wires l8i8 extendinginto an axial opening 22 in the supp rt rod IS. The envelope I is thenclamped in the jaws of a holder 3| and it is lowered until the reducedopen end or neck portion 23 thereof rests on the flange 2|. A coil 24,which is connected to a suitable source 32 of high frequency current, isthen slowly raised by a lever 33, for example,

o as to surround the disc 20, thereby heating the said disc by inductionto a very high degree and causing .the envelope neck 23 and flange 21 tobe fused and sealed together. Pressure is preferably applied to theenvelope l0 during the sealing operation, for example, by a suitableweight 25. By this method of sealing the neck 23 of the envelope is notdistorted, nor is the shoulder 26 distorted, nor is any portion of theshort stem l2 distorted. The envelope in and stem l2 are permitted toremain on the disc 20 for a short period after the current flow to coil24 has been interrupted so that the sealed joint is annealed.

By making the flange 2| large enough to extend a short distance beyondthe neck 23 of the bulb, as shown in Fig. 1, a small head 21 may beformed at the sealed joint which may be desirable for preventing thebase from being pulled oil the envelope. In Fig. 2, I have illustratedone form of base comprising a shell 28 of insulating material which isbutted against the shoulder 26 and is attached to'the neck 23 of theenvelope by cement 29, the bead 21 being embedded in said cement. Sincethe shoulder 26 is undistorted, the bases 28 of diflerent lamps arealways uniformly mounted and the overall lengths of the lamps are heldwithin close limits. Each of the bases 28 is in this instance providedwith a pair of pins 30-30 to which are connected the lead-in wiresl6-l6.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. The method of sealing a glass stem tube to the glass envelope of anelectric lamp or similar device which comprises placing adjacent ends ofsaid stem tube and envelope against a disc of material which is capableof being heated by induction and will not adhere to glass and thenheating said disc by induction to cause a portion of the generated heatto flow by conduction to the abutting ends of said stem tube andenvelope to fuse them together.

2. The method of sealing a glass stem tube to the glass envelope of anelectric lamp or similar device which comprises placing adjacent ends ofsaid stem tube and envelope against a disc 01' carbon and then heatingsaid disc by induction to cause a portion of the generated heat to flowby conduction to the abutting ends of said stem tube and envelope tofuse them together.

3. The method of sealing a glass stem tube having a flanged end to theend of the glass envelope of an electric lamp or similar device whichcomprises positioning said stem tube with its flanged end in abuttingrelation with a disc of material which is capable of being heated byinduction and will not adhere to glass, placing said envelope over saidstem tube with its end pre ing against the said flanged end of said stemtube, and then heating said disc by induction to cause a a portion ofthe generated heat to flow by conduction to the abutting ends of saidstem tube and envelope to fuse them together.

4. The method of sealing adjacent ends of glass tubes together whichcomprises arranging said tubes one within another with their adjacentends against a disc of material which is capable of being heated byinduction and will not adhere to glass and then heating said disc byinduction to cause a portion of the generated heat to flow by conductionto the abutting ends of said tubes to fuse them together.

5. The method of sealing adjacent ends of glass tubes together whichcomprises arranging said tubes one within another with their adjacentends in contact and at least one of them abutting against a disc ofmaterial which will not adhere to glass and then heating said disc tocause a portion of the generated heat to flow by conduction to the saidends of said tubes to fuse them together.

6. The method of sealing adjacent ends of glass tubes together whichcomprises arranging said tubes one within another with their adjacentends in contact and at least one of them abutting against a disc ofmaterial which will not adhere to glass and then heating said discelectrically to cause a portion of the generated heat to flow byconduction to the said ends of said tubes to fuse them together.

7. The method of sealing a glass stem tube to the glass envelope of anelectric lamp or similar device which comprises placing adjacent ends ofsaid stem tube and envelope in contact with each other and the end ofone of them against a disc of material which will not adhere to glassand then heating said disc to cause a portion of the generated heat toflow by conduction to the said ends of said stem tube and envelope tofuse them together.

' ARTHUR J. WHITE.

